This invention relates to an arrangement for supplying fuel from a fuel pressure source located on an outside of an engine enclosure to a fuel injector located on an inside of the engine enclosure. The invention also relates to an internal combustion engine provided with such an arrangement and a method for providing an internal combustion engine with such a fuel supply arrangement.
Cost efficiency important in the production of internal combustion engines. One of the steps in the production, at least for diesel engines and similar, is the installation of the fuel injection equipment. The components forming part of such equipment can be complicated and rather expensive, and the equipment can also be complicated and costly to install.
In certain cases, it is necessary to install the fuel injection equipment on an engine such that the source of fuel pressure is located outside the engine whilst the injector receiving the pressurised fuel is located inside the engine, i.e. in a volume inside an engine enclosure subjected to crankcase pressure and the flow of engine oil. Supply of fuel is then needed from the outside to the inside of the engine. A problem with such an installation type is bow to ensure a reliable but cost-effective and simple-to-install seal that seals off the engine-internal volume from the ambient at the point where a fuel pipe or similar enters the internal engine volume.
U.S. Pat. No. 6,394,071 shows an example of a fuel supply system where the cost and complexity is presented to be reduced compared to prior art. The system of U.S. Pat. No. 6,394,071 is, however, still relatively complex containing a number of different fuel pipes etc. Moreover, there has not been paid much intention to the complexity of the installation process.
There is still a need for less complex and less costly fuel injection equipment and for more cost efficient methods for assembling the equipment and installing it onto the engine.
It is desirable to provide a fuel supply system that provides for a more cost efficient production compared to conventional systems.
The invention, according to an aspect thereof, concerns an arrangement for supplying fuel from a fuel pressure source located on an outside of an engine enclosure to a fuel injector located on an inside of the engine enclosure. The arrangement comprises: a fuel pipe for transporting fuel from the fuel pressure source to the fuel injector via an opening in the engine enclosure and a seal for sealing the fuel pipe at the opening.
The invention, according to an aspect thereof, is characterized in that the seal comprises a first part configured for a sealing contact around the fuel pipe and a second part configured for a sealing contact around a sleeve extending around the opening.
Such an arrangement has the advantage that it provides for a proper sealing also when the opening in the engine enclosure, typically in the cylinder head cover, is significantly larger than the fuel pipe, i.e. when the diameter of the opening is much larger than the diameter of the fuel pipe so that a significant void is formed in the radial direction between the pipe and the edge of the opening. In such a situation a conventional sealing adapted for small gaps cannot be used.
An effect of the inventive arrangement is that it allows for the use of fuel pipes in the form of a regular pipe with a fastening device, such as a pipe nut and a cold-formed cone end, pre-installed at each pipe end. The cross sectional dimension of the fastening device of such standard pipes is larger than that of the actual pipe. Such pipes thus require a larger opening in the engine enclosure for its introduction towards the fuel injector and a larger opening require a special sealing solution. Preferably, the seal is pre-installed onto the fuel pipe and, suitably, this is done before forming the ends and installing the pipe nuts so as to allow the seal to be easily slipped onto the pipe. The use of regular pipes with e.g. pipe nuts lowers the cost of the components and makes it possible to simplify the design of the fuel supply system.
A further advantageous effect of an aspect of the invention is that the connection of the pressure source with the pressure receiving apparatus (typically the fuel injector) can be accomplished using a single continuous pipe without intermediate hydraulic connections. This reduces the costs and improves reliability and durability of the high-pressure line between the source and receiver of the pressure.
A further effect of an aspect of the inventive arrangement is that the assembling of the fuel supply system is simplified, see below. This enhances the cost efficiency of the production.
In an embodiment of the invention the arrangement further comprises a flexible element configured to lock the second part of the seal in its intended position around the sleeve. Preferably, the flexible element comprises a resilient closed loop capable of pressing the second part of the seal towards an outer circumference of the sleeve. Preferably, the flexible element comprises a metal spring. This provides for an easy installation and a secure way of locking the second part of the seal, in particular if the sleeve is provided with a groove for holding the flexible element and preferably also the seal in place.
In an embodiment of the invention the first part of the seal is slidably mounted onto the fuel pipe. This way the seal can easily be slided along the pipe into place with its second part around the sleeve after having properly positioned the fuel pipe (e.g. by fastening it to the fuel injector). Preferably, the arrangement comprises a second flexible element, such as a closed metal spring loop, configured to press the first part of the seal towards the fuel pipe.
The use of such a flexible element for the first part of the seal, preferably pre-assembled with the pipe, allows improving slideability of the seal along the pipe whilst providing the required squeeze in as-mounted state for reliable and durable sealing between the seal and the pipe body.
In an embodiment of the invention an inner portion of the second part of the seal is adapted to the outer dimensions of the sleeve and that an inner portion of the first part of the seal is adapted to the outer dimensions of the fuel pipe, wherein the cross section of the inner portion of the second part is significantly larger than the cross section of the inner portion of the first part of the seal. This provides for a proper seal to both the sleeve and the pipe where the sleeve has a larger cross-section than the pipe.
Preferably, the seal forms a single piece of material that surrounds the pipe when mounted onto the pipe. This lowers the risk of leakage. Preferably, the seal is made of an elastomeric material.
In an embodiment of the invention the seal is pre-installed onto the fuel pipe which, preferably, is provided with a pre-installed fastening device, such as a cone-shaped pipe end and a pipe nut, at its end intended to be connected to the fuel injector and a further pre-installed fastening device (or other detail that prevents easy post-installation of seal onto complete pipe, such as a branched fitting) at its end intended to remain outside of the engine enclosure.
Such a combined product, i.e. seal pre-installed on pipe with pipe nuts (or other fastening device) at both ends, forms a ready-to-use product that provides for efficient handling (it can e.g. be purchased as a ready-to-use product) and can be installed in an efficient way on the engine.
The invention also concerns an internal combustion engine comprising an engine enclosure, a fuel receiving component such as a fuel injector located inside the engine enclosure and an opening in the engine enclosure. The inventive engine comprises a sleeve extending around the opening and a fuel supply arrangement as described above.
In an embodiment of the inventive engine the sleeve has a circular cross section and is positioned on an outside of the engine enclosure. Preferably, the sleeve is provided with a groove configured to hold the second part of the seal and/or the flexible element in place. This provides for a secure locking of the seal.
Preferably, the cross section of the opening is significantly larger than the outer cross section of the fuel pipe. This allows a standard pipe with a pre-installed pipe nut or similar to be inserted through the opening and thus provides for the use of such pipes.
In an embodiment of the inventive engine one end of the fuel pipe is connected to the fuel injector and the other end to a fuel pressure source located outside of the engine enclosure. Preferably, the fuel pressure source is a common rail in fluid communication with at least one further fuel injector, i.e. the common rail extends along the engine. The inventive concept is particularly advantageous for such a fuel supply system. Preferably, the engine enclosure comprises a cylinder head cover, wherein the opening is arranged in the cylinder bead cover. Preferably, the openings are arranged in a lower part of the cylinder head cover, wherein an upper part of the cover is removable to allow access to fastening device at the fuel injector.
The invention also concerns a method for providing an internal combustion engine with a fuel supply arrangement comprising a fuel pipe for transporting fuel from a fuel pressure source located outside an engine enclosure to a fuel injector located inside the engine enclosure.
The inventive method comprises the steps of providing a fuel pipe provided with a seal having a first part configured for a sealing contact around the fuel pipe and a second part configured for a sealing contact around a sleeve extending around art opening in the engine enclosure, wherein the seal is movable along the fuel pipe; introducing an injector end of the fuel pipe through the opening and positioning the fuel pipe; moving the seal relative to the fuel pipe to a position in which the second part of the seal is positioned around and in contact with the sleeve.
Such a method makes the installation procedure efficient and much less complex than described in, for instance, U.S. Pat. No. 6,394,071.
The inventive method can include one or several of the following:                providing a flexible element configured to lock the second part of the seal in its intended position around the sleeve; and arranging the flexible element around the sleeve and the second part of the sealing,        connecting the injector end of the fuel pipe to the fuel injector,        connecting an outer end of the fuel pipe to a fuel pressure source located outside of the engine enclosure,        wherein at least the injector end of the fuel pipe is provided with a pre-installed fastening device, such as a coned end and a pipe nut (which has a larger cross sectional dimension than the fuel pipe),        wherein the flexible element comprises a resilient closed loop capable of pressing the second part of the seal towards an outer circumference of the sleeve, the method comprising the steps of: providing the flexible element around the fuel pipe or the sleeve and; moving the flexible element relative to the fuel pipe to its position in which it locks the second part of the seal around the sleeve, and/or        positioning the seal around the fuel pipe and providing each end of the fuel pipe with fastening device.        
In the last step a ready-to-use pipe-seal component is formed, which step may be carried out at another location by e.g. a subcontractor.